Simulation and experiment of dry ice jet freezing on seedless lychee

In this study, a method utilizing dry ice jet for rapid freezing of seedless lychee is proposed. A rectangular rapid freezing chamber for dry ice jet freezing of lychee is designed. The temperature field and velocity field of lychee freezing process by dry ice jet in the rapid freezing chamber are simulated using COMSOL software. The effects of different inlet velocities (0.16 m/s, 0.20 m/s, 0.24 m/s, 0.28 m/s, 0.32 m/s), inlet radii (15 mm, 20 mm, 25 mm, 30 mm, and 35 mm), lychee arrangement, and tray perforation radii (5 mm, 8 mm, 10 mm) on the lychee freezing process are investigated. Additionally, a fan is installed at the bottom of the rapid freezing chamber to study the effect of velocities of fluid driven by the fan (0.5 m/s, 1.0 m/s, 1.5 m/s) on the freezing process, and compared with the freezing process without a fan. Results show that with increasing dry ice inlet velocity and inlet radius, the time required for lychee to reach freezing requirements decreases. The optimal freezing effect is achieved with an inlet velocity of 0.24 m/s, inlet radius of 15 mm, tray perforation radius of 8 mm, and lychee placement near the perforation hole. The addition of a fan has shortened the freezing time and improved the uniformity of freezing. When the velocity of fluid driven by the fan is 1.0 m/s, the enhancement effect on the freezing process of dry ice jet freezing lychee is relatively optimal. The experimental results are in good agreement with the simulation results, which lays a foundation for the popularization and application of Litchi dry ice jet freezing technology.